# Copyright (c) 2010-2012 OpenStack Foundation # # Licensed under the Apache License, Version 2.0 (the "License"); # you may not use this file except in compliance with the License. # You may obtain a copy of the License at # # http://www.apache.org/licenses/LICENSE-2.0 # # Unless required by applicable law or agreed to in writing, software # distributed under the License is distributed on an "AS IS" BASIS, # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or # implied. # See the License for the specific language governing permissions and # limitations under the License. """ Why our own memcache client? By Michael Barton python-memcached doesn't use consistent hashing, so adding or removing a memcache server from the pool invalidates a huge percentage of cached items. If you keep a pool of python-memcached client objects, each client object has its own connection to every memcached server, only one of which is ever in use. So you wind up with n * m open sockets and almost all of them idle. This client effectively has a pool for each server, so the number of backend connections is hopefully greatly reduced. python-memcache uses pickle to store things, and there was already a huge stink about Swift using pickles in memcache (http://osvdb.org/show/osvdb/86581). That seemed sort of unfair, since nova and keystone and everyone else use pickles for memcache too, but it's hidden behind a "standard" library. But changing would be a security regression at this point. Also, pylibmc wouldn't work for us because it needs to use python sockets in order to play nice with eventlet. Lucid comes with memcached: v1.4.2. Protocol documentation for that version is at: http://github.com/memcached/memcached/blob/1.4.2/doc/protocol.txt """ import six import six.moves.cPickle as pickle import json import logging import time from bisect import bisect from hashlib import md5 from eventlet.green import socket from eventlet.pools import Pool from eventlet import Timeout from six.moves import range from swift.common import utils DEFAULT_MEMCACHED_PORT = 11211 CONN_TIMEOUT = 0.3 POOL_TIMEOUT = 1.0 # WAG IO_TIMEOUT = 2.0 PICKLE_FLAG = 1 JSON_FLAG = 2 NODE_WEIGHT = 50 PICKLE_PROTOCOL = 2 TRY_COUNT = 3 # if ERROR_LIMIT_COUNT errors occur in ERROR_LIMIT_TIME seconds, the server # will be considered failed for ERROR_LIMIT_DURATION seconds. ERROR_LIMIT_COUNT = 10 ERROR_LIMIT_TIME = 60 ERROR_LIMIT_DURATION = 60 def md5hash(key): if not isinstance(key, bytes): if six.PY2: key = key.encode('utf-8') else: key = key.encode('utf-8', errors='surrogateescape') return md5(key).hexdigest().encode('ascii') def sanitize_timeout(timeout): """ Sanitize a timeout value to use an absolute expiration time if the delta is greater than 30 days (in seconds). Note that the memcached server translates negative values to mean a delta of 30 days in seconds (and 1 additional second), client beware. """ if timeout > (30 * 24 * 60 * 60): timeout += time.time() return int(timeout) def set_msg(key, flags, timeout, value): if not isinstance(key, bytes): raise TypeError('key must be bytes') if not isinstance(value, bytes): raise TypeError('value must be bytes') return b' '.join([ b'set', key, str(flags).encode('ascii'), str(timeout).encode('ascii'), str(len(value)).encode('ascii'), ]) + (b'\r\n' + value + b'\r\n') class MemcacheConnectionError(Exception): pass class MemcachePoolTimeout(Timeout): pass class MemcacheConnPool(Pool): """ Connection pool for Memcache Connections The *server* parameter can be a hostname, an IPv4 address, or an IPv6 address with an optional port. See :func:`swift.common.utils.parse_socket_string` for details. """ def __init__(self, server, size, connect_timeout): Pool.__init__(self, max_size=size) self.host, self.port = utils.parse_socket_string( server, DEFAULT_MEMCACHED_PORT) self._connect_timeout = connect_timeout def create(self): addrs = socket.getaddrinfo(self.host, self.port, socket.AF_UNSPEC, socket.SOCK_STREAM) family, socktype, proto, canonname, sockaddr = addrs[0] sock = socket.socket(family, socket.SOCK_STREAM) sock.setsockopt(socket.IPPROTO_TCP, socket.TCP_NODELAY, 1) with Timeout(self._connect_timeout): sock.connect(sockaddr) return (sock.makefile('rwb'), sock) def get(self): fp, sock = super(MemcacheConnPool, self).get() if fp is None: # An error happened previously, so we need a new connection fp, sock = self.create() return fp, sock class MemcacheRing(object): """ Simple, consistent-hashed memcache client. """ def __init__(self, servers, connect_timeout=CONN_TIMEOUT, io_timeout=IO_TIMEOUT, pool_timeout=POOL_TIMEOUT, tries=TRY_COUNT, allow_pickle=False, allow_unpickle=False, max_conns=2, logger=None): self._ring = {} self._errors = dict(((serv, []) for serv in servers)) self._error_limited = dict(((serv, 0) for serv in servers)) for server in sorted(servers): for i in range(NODE_WEIGHT): self._ring[md5hash('%s-%s' % (server, i))] = server self._tries = tries if tries <= len(servers) else len(servers) self._sorted = sorted(self._ring) self._client_cache = dict(((server, MemcacheConnPool(server, max_conns, connect_timeout)) for server in servers)) self._connect_timeout = connect_timeout self._io_timeout = io_timeout self._pool_timeout = pool_timeout self._allow_pickle = allow_pickle self._allow_unpickle = allow_unpickle or allow_pickle if logger is None: self.logger = logging.getLogger() else: self.logger = logger def _exception_occurred(self, server, e, action='talking', sock=None, fp=None, got_connection=True): if isinstance(e, Timeout): self.logger.error("Timeout %(action)s to memcached: %(server)s", {'action': action, 'server': server}) elif isinstance(e, (socket.error, MemcacheConnectionError)): self.logger.error( "Error %(action)s to memcached: %(server)s: %(err)s", {'action': action, 'server': server, 'err': e}) else: self.logger.exception("Error %(action)s to memcached: %(server)s", {'action': action, 'server': server}) try: if fp: fp.close() del fp except Exception: pass try: if sock: sock.close() del sock except Exception: pass if got_connection: # We need to return something to the pool # A new connection will be created the next time it is retrieved self._return_conn(server, None, None) now = time.time() self._errors[server].append(time.time()) if len(self._errors[server]) > ERROR_LIMIT_COUNT: self._errors[server] = [err for err in self._errors[server] if err > now - ERROR_LIMIT_TIME] if len(self._errors[server]) > ERROR_LIMIT_COUNT: self._error_limited[server] = now + ERROR_LIMIT_DURATION self.logger.error('Error limiting server %s', server) def _get_conns(self, key): """ Retrieves a server conn from the pool, or connects a new one. Chooses the server based on a consistent hash of "key". """ pos = bisect(self._sorted, key) served = [] while len(served) < self._tries: pos = (pos + 1) % len(self._sorted) server = self._ring[self._sorted[pos]] if server in served: continue served.append(server) if self._error_limited[server] > time.time(): continue sock = None try: with MemcachePoolTimeout(self._pool_timeout): fp, sock = self._client_cache[server].get() yield server, fp, sock except MemcachePoolTimeout as e: self._exception_occurred( server, e, action='getting a connection', got_connection=False) except (Exception, Timeout) as e: # Typically a Timeout exception caught here is the one raised # by the create() method of this server's MemcacheConnPool # object. self._exception_occurred( server, e, action='connecting', sock=sock) def _return_conn(self, server, fp, sock): """Returns a server connection to the pool.""" self._client_cache[server].put((fp, sock)) def set(self, key, value, serialize=True, time=0, min_compress_len=0): """ Set a key/value pair in memcache :param key: key :param value: value :param serialize: if True, value is serialized with JSON before sending to memcache, or with pickle if configured to use pickle instead of JSON (to avoid cache poisoning) :param time: the time to live :param min_compress_len: minimum compress length, this parameter was added to keep the signature compatible with python-memcached interface. This implementation ignores it. """ key = md5hash(key) timeout = sanitize_timeout(time) flags = 0 if serialize and self._allow_pickle: value = pickle.dumps(value, PICKLE_PROTOCOL) flags |= PICKLE_FLAG elif serialize: if isinstance(value, bytes): value = value.decode('utf8') value = json.dumps(value).encode('ascii') flags |= JSON_FLAG elif not isinstance(value, bytes): value = str(value).encode('utf-8') for (server, fp, sock) in self._get_conns(key): try: with Timeout(self._io_timeout): sock.sendall(set_msg(key, flags, timeout, value)) # Wait for the set to complete fp.readline() self._return_conn(server, fp, sock) return except (Exception, Timeout) as e: self._exception_occurred(server, e, sock=sock, fp=fp) def get(self, key): """ Gets the object specified by key. It will also unserialize the object before returning if it is serialized in memcache with JSON, or if it is pickled and unpickling is allowed. :param key: key :returns: value of the key in memcache """ key = md5hash(key) value = None for (server, fp, sock) in self._get_conns(key): try: with Timeout(self._io_timeout): sock.sendall(b'get ' + key + b'\r\n') line = fp.readline().strip().split() while True: if not line: raise MemcacheConnectionError('incomplete read') if line[0].upper() == b'END': break if line[0].upper() == b'VALUE' and line[1] == key: size = int(line[3]) value = fp.read(size) if int(line[2]) & PICKLE_FLAG: if self._allow_unpickle: value = pickle.loads(value) else: value = None elif int(line[2]) & JSON_FLAG: value = json.loads(value) fp.readline() line = fp.readline().strip().split() self._return_conn(server, fp, sock) return value except (Exception, Timeout) as e: self._exception_occurred(server, e, sock=sock, fp=fp) def incr(self, key, delta=1, time=0): """ Increments a key which has a numeric value by delta. If the key can't be found, it's added as delta or 0 if delta < 0. If passed a negative number, will use memcached's decr. Returns the int stored in memcached Note: The data memcached stores as the result of incr/decr is an unsigned int. decr's that result in a number below 0 are stored as 0. :param key: key :param delta: amount to add to the value of key (or set as the value if the key is not found) will be cast to an int :param time: the time to live :returns: result of incrementing :raises MemcacheConnectionError: """ key = md5hash(key) command = b'incr' if delta < 0: command = b'decr' delta = str(abs(int(delta))).encode('ascii') timeout = sanitize_timeout(time) for (server, fp, sock) in self._get_conns(key): try: with Timeout(self._io_timeout): sock.sendall(b' '.join([ command, key, delta]) + b'\r\n') line = fp.readline().strip().split() if not line: raise MemcacheConnectionError('incomplete read') if line[0].upper() == b'NOT_FOUND': add_val = delta if command == b'decr': add_val = b'0' sock.sendall(b' '.join([ b'add', key, b'0', str(timeout).encode('ascii'), str(len(add_val)).encode('ascii') ]) + b'\r\n' + add_val + b'\r\n') line = fp.readline().strip().split() if line[0].upper() == b'NOT_STORED': sock.sendall(b' '.join([ command, key, delta]) + b'\r\n') line = fp.readline().strip().split() ret = int(line[0].strip()) else: ret = int(add_val) else: ret = int(line[0].strip()) self._return_conn(server, fp, sock) return ret except (Exception, Timeout) as e: self._exception_occurred(server, e, sock=sock, fp=fp) raise MemcacheConnectionError("No Memcached connections succeeded.") def decr(self, key, delta=1, time=0): """ Decrements a key which has a numeric value by delta. Calls incr with -delta. :param key: key :param delta: amount to subtract to the value of key (or set the value to 0 if the key is not found) will be cast to an int :param time: the time to live :returns: result of decrementing :raises MemcacheConnectionError: """ return self.incr(key, delta=-delta, time=time) def delete(self, key, server_key=None): """ Deletes a key/value pair from memcache. :param key: key to be deleted :param server_key: key to use in determining which server in the ring is used """ key = md5hash(key) server_key = md5hash(server_key) if server_key else key for (server, fp, sock) in self._get_conns(server_key): try: with Timeout(self._io_timeout): sock.sendall(b'delete ' + key + b'\r\n') # Wait for the delete to complete fp.readline() self._return_conn(server, fp, sock) return except (Exception, Timeout) as e: self._exception_occurred(server, e, sock=sock, fp=fp) def set_multi(self, mapping, server_key, serialize=True, time=0, min_compress_len=0): """ Sets multiple key/value pairs in memcache. :param mapping: dictionary of keys and values to be set in memcache :param server_key: key to use in determining which server in the ring is used :param serialize: if True, value is serialized with JSON before sending to memcache, or with pickle if configured to use pickle instead of JSON (to avoid cache poisoning) :param time: the time to live :min_compress_len: minimum compress length, this parameter was added to keep the signature compatible with python-memcached interface. This implementation ignores it """ server_key = md5hash(server_key) timeout = sanitize_timeout(time) msg = [] for key, value in mapping.items(): key = md5hash(key) flags = 0 if serialize and self._allow_pickle: value = pickle.dumps(value, PICKLE_PROTOCOL) flags |= PICKLE_FLAG elif serialize: if isinstance(value, bytes): value = value.decode('utf8') value = json.dumps(value).encode('ascii') flags |= JSON_FLAG msg.append(set_msg(key, flags, timeout, value)) for (server, fp, sock) in self._get_conns(server_key): try: with Timeout(self._io_timeout): sock.sendall(b''.join(msg)) # Wait for the set to complete for line in range(len(mapping)): fp.readline() self._return_conn(server, fp, sock) return except (Exception, Timeout) as e: self._exception_occurred(server, e, sock=sock, fp=fp) def get_multi(self, keys, server_key): """ Gets multiple values from memcache for the given keys. :param keys: keys for values to be retrieved from memcache :param server_key: key to use in determining which server in the ring is used :returns: list of values """ server_key = md5hash(server_key) keys = [md5hash(key) for key in keys] for (server, fp, sock) in self._get_conns(server_key): try: with Timeout(self._io_timeout): sock.sendall(b'get ' + b' '.join(keys) + b'\r\n') line = fp.readline().strip().split() responses = {} while True: if not line: raise MemcacheConnectionError('incomplete read') if line[0].upper() == b'END': break if line[0].upper() == b'VALUE': size = int(line[3]) value = fp.read(size) if int(line[2]) & PICKLE_FLAG: if self._allow_unpickle: value = pickle.loads(value) else: value = None elif int(line[2]) & JSON_FLAG: value = json.loads(value) responses[line[1]] = value fp.readline() line = fp.readline().strip().split() values = [] for key in keys: if key in responses: values.append(responses[key]) else: values.append(None) self._return_conn(server, fp, sock) return values except (Exception, Timeout) as e: self._exception_occurred(server, e, sock=sock, fp=fp)